Warrior Ancient and Medieval Rules

Hi all. Another question:

In the General Concepts section at the beginning of the army list
books (or on their appropriate clarifications/errata from FHE.com),
it states that "in addition, Knights/Cavalry/Camelry can only be in
units of the same troop category, per 2.23. Being Mounted is not
the same category for this purpose".

However, later in the same section, it states "upgrades allowed
for troops on one line do not prevent mixing such troops where some
are upgraded and others are not."

Question: In some lists, in my case, FW #12, Anglo-Norman, Knights
start off as IrrB HC L, sh. There is the option to upgrade any
Knights to HK.

So, can you have HK front rank, and HC rear rank in the same
body? This is an upgrade for the unit, but stated upgrade changes
the unit's Troop Category (Cavalry vs. Knights).

Inquiring minds want to know.

Thanks,
-Asif Chaudhry